Method and unit for production of a cast component

ABSTRACT

The invention relates to a method for the production of a cast component ( 10 ), in particular a die casting component, preferably made of an aluminum alloy, according to which the cast component ( 10 ) is at least partially subjected to a heat treatment following the molding process and the removal from the mold ( 12 ), wherein the heat treatment of the cast component ( 10 ) is begun within a period of up to 15 minutes after the removal from the mold ( 12 ). In addition, the invention relates to a device by which a cast component ( 10 ) is taken out of the mold ( 12 ) and transported into a heat treatment facility ( 28 ) by means of one and the same transport system (robot  24 ).

The present invention relates to a method as well as a plant for the production of a cast component, in particular a die casting component, preferably made of an aluminum alloy, of the kind indicated in the pre-characterizing parts of claims 1 and 18, respectively.

In methods popular today for production of a cast component, it is usual to remove the cast component from its mold with the cast melt after casting and setting. Therein, the cast component still has a removal temperature of for example 50° to 400° Celsius. The further cooling of the cast components is then usually effected by quenching in resting or agitated air or else in a basin or by spraying with a liquid cooling medium, especially with water, respectively. After the cast component is substantially cooled to a manageable temperature, the casting residues such as for example the gate system are separated and the cast component is coarsely deburred overall. Subsequently, the now present blank of the cast component is usually temporarily stored for several hours or days, before a succeeding heat treatment is made.

Then, the succeeding single-step or two-step heat treatment usually occurs in a separate plant. A majority of mechanic processing steps for example including dressing the cast component or machining flanges, bores or the like mostly complete the production process.

In order to shorten this production process, it is to be taken from WO 03/040423 A1 as already known to implement the annealing treatment of a cast component made of an aluminum silicon alloy as a shock annealing treatment, which consists of a quick heating to an annealing temperature of 400° to 555° Celsius, to which maintaining at this temperature during a dwell time of preferably at least 1.7 to at most 14.8 min follows, whereupon the cast component is forcibly cooled to substantially room temperature.

However, in the known shock annealing treatment, the circumstance is to be considered disadvantageous that—especially also by the quick heating—a very high energy input is required to bring the cast component to the annealing temperature. Moreover, the heat treatment process can be shortened by the known shock annealing treatment, but the production process from the casting process to the completion of the heat treatment is still extremely long altogether.

Therefore, the object of the present invention is to provide a method as well as a plant for production of a cast component, in particular a die casting component, preferably made of an aluminum alloy, of the initially mentioned type, in which the cast component is heat treated far more energy saving and can be manufactured in a considerably reduced production time.

According to the invention, this object is solved by a method as well as a plant for production of a cast component having the features of claims 1 and 18, respectively. Advantageous developments with convenient and non-trivial further developments of the invention are indicated in the respectively dependent claims.

In order to subject the cast component to a heat treatment far more energy-saving and to be able to manufacture it in a considerably reduced production time, in the method according to the invention, it is provided that the heat treatment of the cast component is begun immediately or within a period of up to 15 min after the removal from its mold. In other words, as distinguished from the production processes known from the prior art up to now, according to the invention, it is provided that the cast component is no longer cooled down to ambient or room temperature, respectively, for example by agitated air or by means of a corresponding cooling medium like water after the removal from its mold, but that the setting heat or residual heat of the cast component is rather exploited to heat the cast component again for heat treatment. Therein, the cast component is to be heated again or be subjected to the heat treatment, respectively, particularly starting from a temperature near its removal temperature. Altogether, thus it is apparent that the cast component can be produced particularly inexpensively under economical points of view with the method according to the invention.

It is moreover a further advantage that the temporal and economical expenditure for storing the cast components between the removal and the succeeding heat treatment can now be significantly reduced.

For example, by the heat treatment process, a very high ductility of the cast component is achieved despite of the relatively high hardness of the cast component such that the cast component is suited especially for application in all trackless land vehicles, thus for example in the automobile and motorcycle construction. Therein, as included within the scope of the invention, it is especially to be considered that the heat treatment process can be applied both for the entire cast component and only for component regions—therefore partially.

In an advantageous development of the invention, it is provided that the heat treatment process of the cast component is begun within a period of up to 2 min and preferably within a period of up to 15 s after the removal from its mold. Hereby, it is achieved that the cast component still has a temperature as high as possible near its removal temperature. In a further advantageous development of the invention, hereto, it is provided that the heat treatment process is begun immediately or within a period of 3 to 8 s after the removal, respectively, such that the cast component can be heated at least approximately starting from its removal temperature. It is clear that particularly fast cycle times and a particularly fast production of the cast components can be realized with such a short period.

Additionally, it is an advantage if the heat treatment process can be begun at a temperature of the cast component in a region from 50° to 400° Celsius and preferably above 150° Celsius of the cast component. Hereby, heating of the cast component to the temperature usually ranging within the limits from 400° to 540° Celsius in solution annealing can be achieved extremely economically since the cast component has to be heated by a considerably lower temperature difference than it would be necessary in heating starting from the ambient or room temperature, respectively. Since, thus, only the temperature difference between for example about 150° Celsius in the removal or the introduction of the cast component into the heat treatment facility and about 490° Celsius in the heat treatment of the cast component has to be overcome, an extremely great saving potential of energy and time results such that an extremely economical and moreover ecologically reasonable production method can be realized.

Therein, the production method according to the invention has manifested advantageous especially in die casting of cast components of an aluminum silicon alloy, since a particularly high energy saving potential can be realized there by the reduction of the period between the removal and the subsequent heat treatment of the cast component.

However, as included within the scope of the invention, it is to be considered that the production method according to the invention can of course also be utilized for cast components of other alloys. Besides the employment in a die casting process, therein, especially, it is also conceivable to employ the method according to the invention in sand or chill casting. Furthermore, it would be conceivable to perform the heat treatment of a magnesium cast component and especially of a magnesium die casting component according to the method according to the invention.

In a further development of the invention, moreover, it has manifested advantageous if a casting residue remains on the cast component during the heat treatment process. Hereby, the process step of separation of the casting residue between the removal of the cast component and the contemporarily succeeding heat treatment can be omitted on the one hand, such that the cast component can be introduced into the heat treatment facility for example at the desired high temperature. Moreover, there results the advantage that the casting residue can contribute to the stabilization or stiffening of the cast component in the cooling following the heat treatment—for example the solution annealing—such that lower distortion results. Therein, in particular, the casting residue can then particularly simply be separated from the cast component if it has been quickly cooled down—for example by means of agitated air or by means of a liquid or the like—and accordingly has a yield strength R_(p0.2) of for example approximately 80 N/mm² and an elongation at break A₅ of 10 to 25%. Thus, since the cast component is relatively soft or ductile, respectively, after solution annealing, the separation of the casting residue can be effected without great component distortion.

A further characteristic of the production method according to the invention is that both a single-step soft annealing for example at temperatures around approximately 320° to 440° Celsius and with dwell times around approximately 4 min to 120 min and a two-step method with one solution annealing at for example about 400° to 540° Celsius and a succeeding storage for example at about 140° to 240° Celsius during a storage time of about 15 min up to 10 h can be alternatively effected as the heat treatment process.

The storage of the cast components can also be effected at a later point in time if a corresponding after-treatment with suitable thermal influence is present such as for example in a cathodic dip varnishing for example of the framing of an automobile.

The cast component is heat treated, especially annealed, for example during a dwell time of about 3 to 120 min and preferably during a dwell time of about 12 to 24 min such that an extremely fast production method from the casting process to the completion of the heat treatment or of the annealing, respectively, can be realized.

A particularly short production method or a particularly short annealing can additionally be achieved by bringing the cast component to the dwell temperature in a quick heating process, especially inductively, by means of a burner or in a salt bath.

In further development of the invention, it is particularly advantageous in the heat treatment process to effect not only a separation of the casting residue but rather also dressing the cast component after the annealing and the cooling associated therewith. Since the cast component is relatively softly formed in this process stage, the dressing can be effected without undue forces and stresses of the cast component.

In the development of the invention, a sufficiently fast and low-distortion cooling of the cast component after annealing can be achieved in that it is made by means of agitated air of a fan or the like during a cooling time of about 1 to 8 min and preferably during a cooling time of about 2 to 6 min. Alternatively hereto, the cooling can also be made after annealing, especially the solution annealing, of course also by means of a cooling liquid, especially by means of water.

A further development of the invention furthermore provides that the cast component is temporarily stored in a buffer furnace associated with the heat treatment process after the removal. Hereby, in simple manner, temporary storage of the cast components can be realized, wherein they are to be maintained at least approximately at their removal temperature with a relatively low expenditure of energy.

In the production plant according to claim 18 provided besides the method according to the invention the shortening or simplification of the production method, respectively, is in particular achieved in that the cast component is to be removed from the mold and to be transported into the heat treatment facility by means of one and the same transport system—for example in the form of a robot. In other words, according to the invention, it is provided to position the heat treatment facility—especially a heat treatment furnace or a liquid basin—in the immediate vicinity of the mold such that the cast component can be introduced contemporarily to its removal from the mold.

A particularly low-cost and time-saving production method can therein be realized in that the cast component is to be removed from the mold and to be transported into the heat treatment facility without temporary storage by means of the transport system. Moreover, in this manner, it is achieved that the heat treatment can be begun starting from a relatively high removal temperature of the cast component. Optionally, a buffer furnace can be associated with the heat treatment facility, in which the cast components can be temporarily stored and maintained at temperature. In preferred manner, it is also reachable by the transport system.

It has manifested further advantageous if the transport system includes a gripping means—for example in the form of a robot—with which the cast component is to be retained in the region of a casting residue. The danger of distortion of the cast component due to undue retaining force of the transport system can thus be reduced.

In further development of the invention, moreover, it has manifested advantageous if the cast component is to be brought into the effective range of a cooling facility by means of that transport system, by which the removal of the cast component from the mold and the introduction into the heat treatment facility has already been effected. Then, the cast component is to be cooled down in simple and fast manner through the cooling facility after the heat treatment—for example the solution annealing. Thus, since the cooling facility is also positioned near the mold and the heat treatment furnace, the production plant according to the invention can be provided with extremely low expenditure of space.

Finally, a storage furnace can optionally also be disposed in the vicinity of the mold or of the heat treatment furnace, respectively, such that one and the same transport system can also be used for loading the storage furnace with the cast component.

It is clear that the advantages described in connection with the production method according to the invention also apply to the production plant—and vice versa.

Further advantages, features and details of the invention appear from the following description of an embodiment as well as based on the drawings; they show in:

FIG. 1 a schematic or symbolic construction of the plant, respectively, for production of a cast component, which actually is produced in a die casting process and subsequently is treated in a two-step heat treatment process within a heat treatment facility and a storage furnace; and in

FIG. 2 a schematic diagram of the temporal progress of the temperature of the cast component during the heat treatment.

From FIG. 1, it is apparent that a cast component 10 is actually produced in a die casting process, in which the liquid metal melt is filled into a mold 12 formed as a metallic permanent mold with correspondingly high pressure and with correspondingly short time and high velocity, respectively. Therein, the mold 12 is retained in a corresponding die casting machine 14, through which two mold halves 16, 18 of the mold 12 can be opened and closed, respectively. From a casting chamber 22, the mold 12 is supplied with metal melt from a casting container 20. Therein, an aluminum silicon alloy for example of the type AlSi10Mg is employed in the present die casting process.

After the metal melt is solidified, the cast component 10 is removed after opening the mold halves 16, 18 and ejecting by means of the ejection pins 23 by means of a robot 24. Therein, the robot 24 includes a gripping means 26, with which it can pick up the cast component 10 preferably on a casting residue 32 such as for example the gate system or the like. Hereby, it is ensured that essential regions or the final molding of the cast component 10 is not unnecessarily deformed by the retaining force transmitted by the robot 24 or by the gripping means 26 thereof, respectively.

In the present embodiment, immediately after the removal from its mold 12, the cast component 10 is introduced into a heat treatment facility 28 in the form of a heat treatment furnace, by which actually a solution annealing at a temperature of about 400° to 540° Celsius is performed. By the immediate or contemporary heat treatment, respectively, the cast component 10 still has a temperature of about 50° to 400° Celsius and preferably above 150° to 180° Celsius especially being near the removal temperature in the introduction into the heat treatment furnace 28. Hereby, it is achieved that the cast component 10 has to be heated by a relatively low temperature difference up to the annealing or dwell temperature, respectively.

As included within the scope of the invention, it is to be considered that the heat treatment process does not have to be effected immediately after the removal of the cast component 10 from its mold. Rather, the heat treatment process can also be begun within a period of up to 15 min after the removal from its mold. Therein, it would be conceivable that the cast component 10 is also temporarily stored in a buffer furnace associated with the heat treatment facility 28. Of course, instead of the furnace 28, a heat treatment basin with a salt bath or the like can also be used.

Since the heat treatment is effected immediately or contemporarily after the removal, respectively, the cast component 10 can be removed from the mold 12 and be taken into the heat treatment facility 28 by means of one and the same robot 24. It is clear that it is required for this that the heat treatment facility 28 is disposed in the vicinity of the die casting machine 14 or of the mold 12, respectively.

The heat treatment process itself can be effected relatively briefly due to the cast component 10 introduced into the heat treatment facility 28 already with a temperature near the removal temperature. Actually, the cast component 10 is heat treated, in particular annealed or solution annealed, respectively, during a dwell time of about 3 to 120 min and preferably during a dwell time of about 12 to 24 min. Subsequent to the solution annealing, the cast component 10 can in turn be removed from the heat treatment facility 28 and be brought into the effective range of a fan 30 by the robot 24, by which the cast component 10 is quickly cooled down to approximately ambient or room temperature, respectively, during a cooling time of about 1 to 8 min. Since the casting residue 32 is still present on the cast component 10, it can be retained in simple manner through the casting residue 32 by the gripping means 26 of the robot 24. A further advantage of the casting residue 32 is that, in cooling the cast component 10 by means of the fan 30, it contributes to stabilization thereof and thus reduces the distortion.

After cooling—as actually for example—by means of the fan 30, the present cast component 10 or the aluminum silicon alloy thereof for example has a yield strength R_(p0.2) of about 80 N/mm² and an elongation at break A₅ of about 10 to 25%. Accordingly, the cast component 10 actually is still very soft such that it can be mechanically processed in simple manner by means of a corresponding separation facility 34 in a further process step. In the separation facility 34, the casting residue 32 is now removed from the cast component 10, wherein the relatively soft material contributes to no great distortion arising. In a further process step, optionally, dressing of the molding of the cast component 10 can be effected. The transfer of the cast component 10 into the separation facility 34 can in turn be effected via the gripping means 26 of the robot 24. Moreover, the casting residue 32 can serve as a stop or gauge of the cast component 10, respectively, within the separation unit 34.

After the mechanic processing within the separation facility 34 is completed, the cast component 10 is introduced into a storage furnace 36, in which the cast component 10 is treated for example at a temperature of 140° to 240° Celsius during a storage time of about 15 min up to 10 h. The transfer of the cast component 10 from the separation facility 34 into the storage furnace 36 can in turn be effected via the robot 24.

As indicated by the line 35, the storage furnace 36 does not have to belong to the plant. Rather, it can also stand separately. Moreover, the storage of the cast component 10 can also be effected at a later point in time if a corresponding after-treatment with suitable thermal influence is present such as for example in a cathodic dip varnishing for example of the framing of an automobile. Therein, the cathodic dip varnishing and the storage associated therewith, respectively, can be effected over a period of 15 to 30 min at a temperature in the range from 80° to 240° Celsius or in particular from 160° to 220° Celsius.

As included within the scope of the invention, it is to be considered that especially the removal of the casting residue 32 by means of the separation facility 34 as well as the storage by means of the storage furnace 36 can also be effected with substantial distance of time to the solution annealing within the heat treatment furnace 28 or to the cooling by means of the fan 30.

It is also within the scope of the invention that a worker can also be provided instead of the robot 24, which can take over the removal of the cast component 10 from its mold 12 or the transfer of the cast component within the scope of the further process steps.

Finally, as included within the scope of the invention, it is to be considered that a single-step heat treatment for example by soft annealing at a temperature of about 320° to 440° Celsius during an annealing time of about 4 min to 120 min can also be made instead of the two-step heat treatment process described here. Fundamentally, it is moreover possible that the cast component 10 can be subjected to all of the usual heat treatment processes. In particular, it is conceivable to employ the heat treatment processes T4, T6, T6X, T7 as well as O.

In FIG. 2, a schematic diagram of the temporal progress of the temperature of the cast component 10 during the heat treatment is illustrated. Therein, the temperature progress of a conventionally produced cast component 10 is shown by the line RT, which is heated starting from the ambient temperature T_(Raum) up to the annealing temperature or dwell temperature T_(H), respectively, which is reached after a time t_(RThalt). Additionally, the temperature progress of a cast component 10 produced according to the method described above is shown by the line ET, which is heated starting from a temperature T_(ET) near the removal temperature up to the annealing temperature or dwell temperature T_(H), respectively, which is reached after a time t_(EThalt). Thus, it is apparent from the diagram that the dwell temperature T_(H) is of course reached much earlier starting from the temperature T_(ET) than it is the case from the ambient temperature T_(Raum)—with otherwise the same heating conditions. If for example a correspondingly small dimensioned component is quickly heated in a salt bath, thus, for example already after a time of 5 s, the dwell temperature T_(H) can be reached. In a chamber furnace, a correspondingly great dimensioned component can reach its annealing temperature or dwell temperature T_(H), respectively, even only after a longer time, for example after 30 min.

Moreover, it is appreciable that, starting from the temperature T_(ET), a molding temperature T_(Einf) is also reached much earlier than starting from the ambient temperature T_(Raum), namely at a time t_(ETeinf) as opposed to a time t_(RTeinf). Therein, the molding temperature T_(Einf) determines that temperature from which in solution annealing for example of an aluminum silicon casting alloy the silicon present needle-shaped or plate-shaped, respectively, in the AlSi eutectic after the casting process or before the heat treatment, respectively, is correspondingly molded or rounded off, respectively. Hereby, the considerably improved morphology of the cast component 10 results, which for example results in an increased ductility and optionally in a reduced hardness. 

1. A method for production of a cast component, in particular a die casting component, preferably made of an aluminum alloy, in which the cast component is at least partially subjected to a heat treatment process subsequent to the casting process and the removal from its mold, wherein the heat treatment process of the cast component is begun within a period of up to 15 min after the removal from its mold.
 2. The method according to claim 1, wherein the heat treatment process of the cast component is begun within a period of up to 2 min and preferably within a period of up to 15 s after the removal from its mold.
 3. The method according to claim 1, wherein the heat treatment process is begun at a temperature of the cast component in a region of 50°-400° Celsius.
 4. The method according to claim 1, wherein a casting residue remains on the cast component during the heat treatment process.
 5. The method according to claim 1, wherein the heat treatment process is selected from the group consisting of a single step soft annealing and a solution annealing with subsequent storage.
 6. The method according to claim 1, wherein the heat treatment process is performed in one of the following from the group consisting of a heat treatment furnace and a heat treatment bath.
 7. The method according to claim 4, wherein the casting residue is removed from the cast component after annealing and cooling down associated therewith.
 8. The method according to any one of claim 5, further comprising the step of: dressing of the cast component after the annealing and the cooling down associated therewith.
 9. The method according to claim 5, wherein cooling after the annealing, in particular the solution annealing, is made by means of agitated air during a cooling time of about 1 to 8 min and preferably during a cooling time of about 2 to 6 min.
 10. The method according to claim 5, wherein cooling after the annealing, in particular the solution annealing, is made by means of a cooling liquid, in particular by means of water.
 11. The method according to claim 5, wherein after the annealing, in particular the solution annealing and the cooling down associated therewith, storage of the cast component is made at a temperature of 140° to 240° Celsius during a storage time of about 15 min up to 10 h.
 12. The method according to claim 5, wherein storage of the cast component is made at a later point in time after the annealing, in particular by cathodic dip varnishing.
 13. The method according to claim 5, wherein soft annealing is made at a temperature of about 320° to 440° Celsius during an annealing time of about 4 to 120 min.
 14. The method according to claim 1, wherein, after the removal, the cast component is temporarily stored in a buffer furnace associated with the heat treatment process.
 15. The method according to claim 14, wherein the cast component is at least approximately maintained at its removal temperature in the buffer furnace.
 16. The method according to claim 5, wherein the cast component is heat treated, in particular annealed, during a dwell time of about 3 to 120 min and preferably during a dwell time of about 12 to 24 min.
 17. The method according to claim 5, wherein the cast component is brought to a dwell temperature in a quick heating process, in particular inductively, by means of one selected from the group consisting of a burner and a salt bath.
 18. A plant for production of a cast component, in particular a die casting component, preferably made of an aluminum alloy, including a mold from which the cast component is to be removed subsequent to the casting process, wherein the cast component is to be removed from the mold and to be transported into a heat treatment facility by means of one and the same transport system.
 19. The plant according to claim 18, wherein the cast component is to be removed from the mold and to be transported into the heat treatment facility by means of the transport system without temporary storage.
 20. The plant according to claim 18, wherein a heat treatment furnace or a heat treatment basin is associated with the heat treatment facility.
 21. The plant according to claim 18, wherein a buffer furnace is associated with the heat treatment facility, in which the cast component can be temporarily stored.
 22. The plant according to claim 18, wherein a gripping means of the transport system is provided, by which the cast component is to be retained in the region of a casting residue.
 23. The plant according to claim 18, wherein subsequent to the heat treatment, the cast component is to be brought into the effective range of a cooling facility by means of the transport system.
 24. The plant according to claim 18, wherein the cast component is to be brought to a separation unit for mechanic processing by means of the transport system.
 25. The plant according to claim 18, wherein the cast component is to be transported into a storage furnace by means of the transport system. 